Method for producing electrical terminals



July .15, 1969 A. w. SCHMITZ, JR 3,455,022

METHOD FOR PRODUCING ELECTRICAL TERMINALS Original Filed Feb. 14, 1962 FIG. 2.

FIG. 7.

FIG. 5.

INVENTOR; ALFRED W. SCHMITZ, JR

W21 A oruy:

United States Patent US. Cl. 29-629 4 Claims ABSTRACT OF THE DISCLOSURE Conventional terminals or wire connectors in strip form are made readily insulatable by inserting one end of each of a plurality of heat shrinkable dielectric sleeves over one end of each terminal in a strip thereof, so that each terminal projects part way into its associated sleeve. The sleeves are longer than the terminals; and said one end of each sleeve is heat treated to cause it to shrink locally into frictional contact with the associated terminal intermediate its ends. When a terminal is thereafter severed from the strip and crimped to a wire lead, for instance, the sleeve may be slid axially over the crimped end, after which the sleeve is subjected to further heat along its entire length so that it shrinks about the entire terminal and connection.

This is a division of application Ser. No. 173,271, filed Feb. 14, 1962, now Patent No. 3,220,807.

This invention relates to electrical terminals, and more particularly to a method for readily identifying and insulating the terminals.

In the assembly line production of electrical products of the type which include relatively complex wiring systems, it is often necessary to employ numerous wire leads in interconnecting the various electrical elements (resistors, condensors, relays, etc.) employed in a respective system. Each wire lead generally comprises a length of wire which has electrical connectors or terminals secured to the opposite ends thereof, respectively. Conventional terminals are usually of the male or female type, and are adapted to be removably connected to a complementary male or female terminal, respectively.

During the assembly of a product such as an electrical control panel or the like, it is often desirable to individually identify each of the wire leads employed therein so that the worker need not rely on a wiring diagram for directions, but may complete the wiring of a respective circuit merely by connecting similarly identified leads to another. Moreover, since it is often necessary to cram the several wire leads of a respective circuit into a relatively small area in the housing of a product, it is desirable, where possible, to fully insulate the connections between terminals and the respective wire leads connected thereto to prevent any short circuiting of the products electrical system.

It is an object of this invention to provide a method for making a strip of individually identified and readily insulatable terminals.

Another object of this invention is to provide an improved method of identifying and insulating the connections between the wire leads of an electrical circuit.

Other objects of the invention will be apparent hereinafter from the specification and from the recital of the appended claims, particularly when read in conjunction with the accompanying drawing.

In the drawing:

FIG. 1 is an elevational view of part of a strip of terminals made in accordance with one embodiment of this invention, and showing an individually identified insulating sleeve on each terminal, one of which sleeves is cut away in part;

FIG. 2 is an enlarged sectional view taken along the line 2-2 in FIG. 1 and looking in the direction of the arrows;

FIG. 3 is a sectional view, on the same scale as FIG. 2, taken along the line 3-3 in FIG. 1 and looking in the direction of the arrows;

FIG. 4 is an elevational view illustrating how the terminals are severed from one another by removing the portions of the strip shown in broken lines, and how wire leads are secured to the ends thereof opposite the insulating sleeves;

FIG. 5 is an elevational view cut away in part to illustrate how a sleeve may be shifted axially on an individual terminal and shrunk thereabout so that it surrounds both the terminal and a portion of the wire connected thereto, so that it permits a complementary terminal to be inserted in and mechanically connected to the insulated terminal;

FIG. 6 is a cross-sectional view, on the same scale as FIGS. 2 and 3, taken along the line 6-6 in FIG. 5 and' looking in the direction of the arrows; and

FIG. 7 is an elevational view cut away in part to illustrate further how a sleeve on an individual terminal may be shifted axially and shrunk to surround both the individual terminal and a complementary terminal connected thereto.

Heretofore electrical connectors or terminals have been manufactured in strip form, usually by stamping or otherwise machining an elongate strip of metal to provide longitudinally spaced and transversely extending terminals therealong. Such strips are generally purchased by the manufacturers of electrical appliances and the like, whose employees must then secure one end of a wire lead to one end of each terminal, and sever the strips between adjacent terminals. The end of the connector or terminal to which the wire lead is connected is usually performed into a trough-like or Osha-ped socket which may be readily crimped about a wire end to permanently secure the terminal thereto. The opposite end of the terminal is provided with a somewhat similar socket, or merely with a hole, in which one end of a further terminal is adapted to be removably secured, e.g., by friction alone, or by a screw and nut combination. This further terminal at its opposite end may be rigidly fixed to a stationary block, to one outlet of a switch or the like, or it may in turn be connected to one end of a further wire lead. The following invention relates to terminals strips similar to the type described above, but modified to accommodate heat shrinkable plastic sleeves which are mounted on each of the terminals of a strip to provide ready means for identifying and insulating the terminals and the wires connected thereto when the latter are incorporated in a circuit.

Referring now to the drawing by numerals of reference, and first to the embodiment shown in FIG. 1, 12 denotes an elongate strip of metal having a plurality of longitudinally spaced connectors or terminals 11 integral therewith. Each terminal projects both above and below at right angles from both sides of the strip. The upwardly projecting portion of each terminal has marginal portions of its longitudinal sides bent inwardly toward one another until the terminal end is generally C-shaped in cross section, as seen in FIG. 3, thereby providing spaced flaps or projections 13 which overlie the central portion of the terminal and form therewith a socket 14. The downwardly projecting portion of each terminal 11 has marginal portions of its longitudinal sides serrated or otherwise provided with a plurality of spaced, saw tooth projections 15. The projections 15 on opposite sides of a respective terminal .11 are bent slightly toward one another (FIG. 2) to form a further socket 16 in each terminal at the end thereof opposite a respective socket .14. Adjacent the inner ends of the sockets 14, the sides of each terminal taper inwardly toward one another as they approach the portions of strip 12 which interconnect adjacent terminals, whereby terminals 11 have reduced cross-sectional areas or neck portions 17 formed between their sockets 14 and strip 12.

A plurality of heat shrinkable plastic sleeves 21 are mounted on terminals 11 so that one end of each sleeve 21 surrounds a respective terminal socket 14. The sleeves 21 are prepared from heat shrinkable tubing of the type comprising either silicone rubber, vinyl, irradiated polyethylene Teflon or the like; and each sleeve has an identification mark thereon as for instance numerals 1 or 2 as shown in FIGS. 1 and 4. Each sleeve 21 has an axial length greater than the overall length of the respective terminal 11 upon which it is mounted, and initially has an inner diameter large enough to permit a respective sleeve to be readily slid over the end of a terminal 11 defined by the socket 14. A sleeve 21 is first positioned over each socket 14 until its inner end surrounds the neck portion 17 of a respective terminal 11. Thereafter heat is applied to the inner ends of the sleeves so that the inner sleeve ends shrink around portions 17 of the terminals, whereby each sleeve 21 forms a reduced diameter neck portion 22 which is complementary to and which fits into the recess formed by a respective neck portion 17 of a terminal. The aforementioned heating of the sleeves 21 may be accomplished by means of jets of warm air directed at the ends of the sleeves which are to be shrunk, or by any similar means which is capable of localizing the heat applied to the sleeves. Sleeves 2.1 are thus held frictionally over the sockets 14 with the reduced diameter portion 22 of each sleeve lodged between the tapering terminal sides defining the neck 17 of a terminal, and the adjacent portions of strip 12.

When it is desired to employ terminals 11 in a circuit, the strip of interconnected terminals is inserted into the jig or die of a conventional stamping machine (not illustrated) and the bare ends of lead wires 24 are then inserted into the sockets 16 of the terminals. The machine is thereafter actuated to sever and remove the connecting portions of the strip 12 from between the terminals as shown by the broken lines in FIG. 4, and simultaneously to crimp or bend the projections 15 down into locking engagement with the bare ends of the wire leads 24. This severing and crimping step forms the lower end of each terminal between its neck portion 17 and the terminal end of its socket 16 in such manner that the resultant width or outside diameter of each terminal at its lower end is small enough to permit the reduced diameter neck portion 22 of a respective sleeve to be slid thereover.

After the terminals 11 have been severed from one another and the wire leads 24 secured thereto, each sleeve 21 is slid axially on its respective terminal 11 toward the end thereof containing a wire lead 24 for a distance suflicient to permit a further, male, bayonettype terminal 25 to be inserted into the sockets .14 of the terminals 11 as shown in FIGS. and 7. Each terminal 25 is adapted to be frictionally retained in .a socket 14 of a respective terminal 11; and with the terminals thus connected to one another, a portion 26 of each terminal 25 will project from its associated terminal 11. Portions 26 of the terminals 25 may be provided with a socket similar to sockets 16 of terminals 11, and lead wires 27 may be secured therein. When the terminals 11 and 25 are connected to one another, each sleeve 21 is again shifted axially until one end thereof is substantially flush with the outer, terminal end of the socket 14, and the other end thereof extends over part of the wire lead 24 extending from the opposite end of the terminal as shown in FIG. 5; or each sleeve is shifted until it completely surrounds both terminals .11 and 25 and portions of the wires 24 and 27 projecting therefrom, as shown in FIG. 7. Each sleeve 21 is then heated along its entire length so that it shrinks to conform snugly about the respective portions of the terminals and lead wires which it surrounds.

When the sleeve 21 is positioned as shown in FIG. 5, socket 14 in each terminal remains accessible so that the male type terminal 25 may be inserted into or withdrawn from each of the sockets 14 as desired. Moreover, in such position, sleeve 21 not only effectively insulates the entire terminal 11 and the bare end of the wire lead 24 secured therein, but also insulates any bare portion .of the lead, such .as shown at 28 in FIGS. 4, 5 and 7, which is not confined within socket 16. Furthermore, the sleeve reinforces and supports the wire lead 24 adjacent the point at which it is connected to terminal 11, thereby minimizing any cold working stresses which might otherwise be set up in portion 28 of the wire when it is subjected to bending action at the point where it enters socket 16. The positioning of sleeve 21 as shown in FIG. 5 is most desirable in those instances in which the male terminal 25 assumes a substantially stationary position in a circuit, in which case the portion 26 thereof which is not insulated by sleeve '21 will have little tendency to be moved into short circuiting engagement with another wire or terminal in the circuit.

The method of completely insulating the mechanically connected terminals 11 and 25 as shown in FIG. 7 is particularly useful in those instances wherein a plurality of wire leads are employed in a circuit in such manner that the mechanically connected terminals joining any two leads may tend to accidentally pull apart or brush against another such connection during operation of the circuit. In such case the plastic sleeve 21 would serve not only to reinforce the mechanical connection between terminals 11 and 25 to eliminate accidental separation thereof, but also would insulate and support the connections between the wire leads 24 and 27 and, in their respective terminals 11 and 25.

From the foregoing it Will be apparent that applicants novel method provides a ready means for expediting the assembly line production of relatively complex circuits. For instance, it has heretofore been the practice of manufacturers to purchase strips of insulators and distribute them to assembly line workers who then separated the terminals and connected wires thereto as shown in FIG. 2. In this old method, the worker had neither a ready means to identify wire leads, nor means to adequately insulate connections therebetween. However, the strips of terminals may now be prepared for the manufacturer with sleeves 21 thereon already identified in accordance with his instructions (for instance, with certain of the sleeves of a single strip identified differently as shown in FIG. 1, or with all the sleeves in a single strip similarly identified); and which sleeves provide the assembly line worker with a ready means for identifying terminals and wire leads, and insulating connections therebetween.

While the invention has been described as being particularly adaptable to the type of terminal which is formed with a socket at one end for receiving a male, bayonet-type terminal, it is to be understood that sleeves 21 could be employed in combination with a strip of terminals formed with terminal receiving sockets of a shape different than those illustrated by sockets 14 herein. Similarly, it is to be understood that the shape of the wire receiving socket 16 can be altered without departing from this invention. Moreover, while it is preferred to manufacture the strip of terminals with the sleeves disposed over the sockets 14, it is within the scope of this invention to position the reduced diameter ends of sleeves 21 over the wire receiving sockets 16 of the terminals in those instances where, before being crimped or bent into engagement with the bare ends of wire leads, the wire receiving sockets have a greater cross sectional area or are larger in breadth than the terminal receiving sockets 14. Moreover, while the sleeves 21 have been illustrated with identifying numerals thereon it is to be understood that the sleeves may be marked for individual identification by other means, such as by inscribing letters thereon, using sleeves of different colors, or such means for affording ready identification thereof.

While the invention has been described in connection with a specific embodiment thereof, it will be understood that it is capable of further modification, and this application is intended to cover any variations, uses, or adaptations of the invention following, in general, the principles of the invention and including such departures from the present disclosure as come within known or customary practice in the art to which the invention pertains and as may be applied to the essential features hereinbefore set forth, and as fall within the scope of the invention or the limits of the appended claims.

Having thus described my invention, what I claim is:

1. The method of making readily insulatable terminals, comprising:

(a) providing an elongate strip of metal having identical, longitudinally spaced and transversely extending terminals integral therewith, said terminals being severable from said strip for use as wire connectors in an electrical circuit,

(b) providing a plurality of heat shrinkable dielectric sleeves each of which has an axial length greater than the length of each terminal, and an internal diameter larger than the maximum width of at least one end of each terminal,

(c) positioning said sleeves over said one end of the terminals so that each terminal extends partway into one end of a respective sleeve, and

(d) heating each sleeve at said one end only thereof thereby to shrink the last-named ends into frictional engagement with said terminals intermediate the ends thereof to retain the sleeves thereon.

2. The method of insulating electrical terminals and wire leads connected thereto, comprising:

(a) providing at least one electrical terminal having a first socket in one end thereof in which a further terminal is adapted to be secured, and a further socket in the opposite end thereof in which one end of a wire lead is adapted to be secured,

(b) positioning one end of a heat-shrinkable dielectric sleeve, which has an axial length greater than the length of said one terminal, over said socket in said one end of said one terminal.

(c) applying heat to said one end of said sleeve to cause the last-named end to shrink around said one terminal intermediate said sockets,

(d) securing one end of a wire lead in said further socket,

(e) shifting said sleeve axially on said one terminal in the direction of said further socket until said sleeve completely surrounds said one terminal and a portion of the wire lead projecting therefrom, and thereafter i(f) applying heat to the full axial length of said sleeve to cause it to shrink snugly around said one terminal and said portion of the wire lead which it surrounds.

3. The method of insulating electrical terminals and wire leads connected thereto, comprising:

(a) providing at least one electrical terminal having a first socket in one end thereof in which a further terminal is adapted to be secured, and a further socket in the opposite end thereof in which one end of a 'wire lead is adapted to be secured,

(b) positioning one end of a heat shrinkable plastic sleeve, which has an axial length greater than the length of said one terminal, over said socket in said one end of said one terminal,

(c) applying heat to said one end of said sleeve to cause the last-named end to shrink around said one terminal intermediate said sockets,

(d) securing one end of a wire lead in said further socket,

(e) shifting said sleeve axially on said one'terminal in the direction of said further socket to afford access to said first socket,

(f) providing a further terminal having a further wire lead projecting from one end thereof,

(g) securing the opposite end of said further terminal in said first socket,

(h) shifting said sleeve axially until it surrounds both said terminals and portions of the wire leads projecting therefrom, and thereafter,

(i) applying heat to the full axial length of said sleeve to cause it to shrink snugly around and completely insulate said further terminal, said one terminal and said portions of the lead wires which it surrounds.

4. The method of forming readily identifiable and insulated connections between wire leads and terminals, comprising:

(a) providing an elongate strip of metal having identical, longitudinally spaced and transversely extending terminals integral therewith,

(b) providing a plurality of heat shrinkable plastic sleeves each of which has an identification mark thereon, and each of which has an axial length greater than the length of a terminal,

(c) positioning said sleeves over the terminals so that each terminal extends part way into one end of a respective sleeve,

(d) applying heat to each sleeve adjacent said one end thereof to shrink the last-named ends into frictional engagement with said terminals to retain the sleeves thereon,

(e) securing one end of a wire lead to one end of each terminal,

(f) removing the portions of the strip between said spaced terminals,

(g) sliding said sleeves axially on said terminals until each sleeve surrounds its respective terminal and a portion of the wire projecting therefrom, and thereafter (h) applying heat to each sleeve along its length to cause it to shrink snugly about its terminal and the portion of the lead wire it surrounds.

References Cited UNITED STATES PATENTS 3,157,449 11/ 1964 Hennessey 29-447 2,715,764 8/1955 Pierce. 3,040,3 6/ 1962 Folta 174-84 FOREIGN PATENTS 883,155 11/ 1961 Great Britain.

JOHN F. CAMPBELL, Primary Examiner R. W. CHURCH, Assistant Examiner US. Cl. X.R. 29447, 628; 174-84; 206-56 

